CLUSTER  summary

Description: ESA's Cluster II mission consists of four identical spacecraft flying in formation high above the Earth's poles. It is a replacement of the original Cluster mission which was lost in a launch failure during the maiden flight of the Ariane 5 rocket on 4 June 1996. The new Cluster mission was launched in 2000. Due to its success, the original two-year mission has been extended twice, first through 2005 and then through 2009.

Objectives: Cluster  is part of an international collaboration to investigate the physical connection between the Sun and Earth. Flying in a tetrahedral (triangular pyramid) formation, the four spacecraft will collect the most detailed data yet on small-scale changes in near-Earth space and the interaction between the charged particles of the solar wind and Earth's atmosphere. This will enable scientists to build a three-dimensional model of the magnetosphere and to better understand the processes taking place inside it.

Scientific results: An enormous lot! See the list of Cluster top stories at ESA.

How the mission was named: The name Cluster was chosen because of the way the four spacecraft will fly in a group around the Earth. When studies demonstrated that it would be possible to reuse some parts and to fly four spacecraft which were almost identical to those which were lost, the replacement mission was named Cluster II

Industrial involvement: Prime contractor for Cluster was Dornier Satellitensysteme GmbH, Friedrichshafen, Germany, the leader of an industrial consortium involving 35 major contractors from all of the ESA member countries and the United States

Launch date: July 16 and August 9  2000

Launcher: Two Russian Soyuz launchers with a Fregat upper stage, provided by the Russian-French Starsem consortium

Satellite names: The satellites have been named Salsa, Samba, Rumba and Tango

Satellite launch mass: Approximately 1 200 kg each (fully fuelled) including 71 kg of scientific payload

Dimensions: Main spacecraft diameter 2.9  m, height 1.3  m. Each also carries two antenna booms, two 5 m experiment booms and four 50  m experiment wire booms

Payload: Each spacecraft carries an identical set of 11 instruments to investigate charged particles, electrical and magnetic fields i.e. space weather. These were built by European and American instrument teams led by Principal Investigators

Orbit: Elliptical polar orbit, 19 000 to 119 000 km, 57 hour period.

Spacecraft operations centre: European Space Operations Centre (ESOC), Germany

Ground station: Villafranca, Spain

Science operations centre: Joint Science Operations Centre at Rutherford Appleton Laboratory, Didcot, UK

Foreseen operational duration: 27 months

Cost: 315 million Euros at 1999 economic conditions (including manufacturing, launch and operations of the Cluster II spacecraft, and 40% of the funding for the payload)

Spacecraft vital statistics

Diameter: 2.9 m
Height: 1.3 m
Mass: 1 200 kg
(of which) Propellant: 650 kg
(of which) Scientific payload: 71 kg
Solar array power: 224 W
Spin rate: 15 rpm
Operational lifetime: 2 years

Soyuz launcher facts

Lift off weight: 304 tonnes
(of which) Propellant weight: 279.5 tonnes
Height: 43.5 m
Maximum diameter: 10.3 m
Thrust (in vacuum)
- first stage: 4 964 kN
- second stage: 997 kN
- third stage: 298 kN
- fourth stage (Fregat): 19.6 kN
Payload capability (to 400 km): up to 6 tonnes

Launcher facts: the Fregat upper stage

Diameter: 3.35 m
Height: 1.5 m
Lift off weight: 6 415 kg
(of which) Propellant weight: 5 350 kg
- fuel: Unsymmetrical dimethyl-hydrazine (UDMH)
- oxidizer: Nitrogen tetroxide
Main engine thrust: 19 620 N
last modified on Tuesday, 23-May-2006 09:42:44 CEST